1. Field of the Invention
The present invention relates to a pipe which can be manufactured by molding a plate member into a cylindrical-shaped member and then connecting one side edge portion of the cylindrical-shaped member and the other side edge portion thereof to each other.
2. Description of the Related Art
Recently, in a heat exchanger such as a capacitor or the like, a tank main body is manufactured from a pipe member which is formed of aluminum.
And, conventionally, such pipe member is manufactured in such a manner that, as shown in FIG. 6, a plate member 11 is molded into a cylindrical-shaped member and, after then, one side edge portion 11a of the cylindrical-shaped member and the other side edge portion 11b thereof are connected together by brazing R.
However, in such conventional pipe member 13, if the pipe member 13 is heated up to a high temperature within a brazing furnace for the purpose of brazing, then, as shown in FIG. 7, with a point A as the center thereof, one side edge portion 11a and the other side edge portion 11b of the pipe member 13 are opened, which makes it difficult to braze together one side edge portion 11a and the other side edge portion 11b of the pipe member 13 with accuracy.
In view of this, conventionally, as shown in FIG. 8, there is employed a method in which one side edge portion 11a and the other side edge portion 11b of the pipe member 13 are previously spot welded W together at intervals and, after then, one side edge portion 11a and the other side edge portion 11b of the pipe member 13 are brazed to each other.
However, in the above-mentioned conventional manufacturing method, because one side edge portion 11a and the other side edge portion 11b of the pipe member 13 are previously spot welded W together at intervals, there arises a problem that a large number of man-hours are necessary to manufacture the pipe member 13.
Conventionally, as a method which has solved this problem, there are known a pipe and a method for manufacturing the same as follows.
FIGS. 9 to 11 respectively show the above-mentioned pipe; that is, this pipe is manufactured in such a manner that a plate member 15 is molded into a cylindrical-shaped member, and one side edge portion 15a and the other side edge portion 15b of the cylindrical-shaped member are connected to each other to thereby form a pipe main body 17.
Also, as shown in FIG. 9, in the pipe main body 17, there are formed a plurality of fitting portions 19 which are spaced at given intervals from one another.
Each of the fitting portions 19, as shown in FIG. 10, includes a securing portion 21 which is formed integrally with one side edge portion 15a of the pipe main body 17, and a caulking pawl portion 23 which is formed integrally with the other side edge portion 15b of the pipe main body 17 and also with which the securing portion 21 can be fitted from inside.
And, the leading end portion 23a of the caulking pawl portion 23 is bent and is stored in a securing recessed portion 25 formed on the side of one side edge portion 15a of the pipe main body 17.
In the present pipe, if the securing portion 21 formed integrally with one side edge portion 15a of the pipe main body 17 is fitted with the caulking pawl portion 23 formed integrally with the other side edge portion 15b of the pipe main body 17, then one side edge portion 15a and the other side edge portion 15b of the pipe main body 17 can be positively contacted together at a given position thereof, with the result that one side edge portion 15a and the other side edge portion 15b of the pipe main body 17 can be positively connected together at a given position without using spot welding.
Also, since the leading end portion 23a of the caulking pawl portion 23 is stored in a securing recessed portion 25 formed on the side of one side edge portion 15a of the pipe main body 17, the leading end portion 23a of the caulking pawl portion 23 is prevented from projecting beyond the outer periphery of the pipe main body 17, thereby being able to manufacture a pipe which is entirely free from troublesome projections.
However, in this pipe, as shown in FIG. 9, because the width W of the side surface portion 23b of the caulking pawl portion 23 is set equal to the width W of the leading end portion 23a thereof, when the leading end portion 23a of the caulking pawl portion 23 is bent, as shown in FIG. 12, the bent portion 23c of the caulking pawl portion 23 provides a relatively large arc shape. This raises a problem that it is difficult for the leading end portion 23a of the caulking pawl portion 23 to hold the-securing portion 21 positively.
In view of the above, a pipe shown in FIG. 13 which can solve the above-mentioned problem has been previously developed.
Here, FIG. 13 shows the details of the main portions of the pipe disclosed in the present cited publication; in particular, in this pipe, the width H1 of the side surface portion 27b of a caulking pawl portion 27 in the longitudinal direction thereof is set larger than the width H2 of the leading end portion 27a of the caulking pawl portion 27 in the longitudinal direction thereof.
Also, the leading end portion 27a is formed in the central portion of the side surface portion 27b, while the two edges 27c of the leading end portion 27a are formed at positions spaced apart from the two edges 27d of the side surface portion 27b.
That is, in the present pipe, because the width H1 of the side surface portion 27b of the caulking pawl portion 27 in the longitudinal direction thereof is set larger than the width H2 of the leading end portion 27a of the caulking pawl portion 27 in the longitudinal direction thereof, the rigidity of the leading end portion 27a is sufficiently lower than the rigidity of the side surface portion 27b, and also because the two edges 27c of the leading end portion 27a are formed at positions spaced apart from the two edges 27d of the side surface portion 27b, the two edges 27c of the root portion 27e, which is connected to the side surface portion 27b, of the leading end portion 27a are weak in strength. Due to these two factors, the leading end portion 27a of the caulking pawl portion 27 can be bent at and from the base portion 27e thereof into a given shape.
That is, the leading end portion 27a of the caulking pawl portion 27 can be bent into a given shape easily and positively.
However, in the above-mentioned pipe, as shown in FIG. 14, there is a possibility that the caulking pawl portion 27 can be situated in the neighborhood of the end portion of the pipe main body 28 thereof. In this case, when the cylindrical-shaped portion 29a of a cap 29 is fitted with the outer periphery of either end of the pipe main body 28, the cylindrical-shaped portion 29a of the cap 29 interferes with the edge of the side surface portion 27b of the caulking pawl portion 27, which makes it difficult to bring the cylindrical-shaped portion 29a of the cap 29 into fitting engagement with the pipe main body 28 with accuracy.
That is, in this pipe, the pipe main body 28 must provide different lengths according to uses but, for easy manufacture and design of the pipe, it is desirable that the setting position of the caulking pawl portion 27 to be formed in the pipe main body 28 can be used in common as much as possible. Therefore, depending on the length that is required of the pipe main body 28, there is a fear that the cylindrical-shaped portion 29a of the cap 29 can interfere with the edge of the side surface portion 27b of the caulking pawl portion 27.